A REMARKABLE FOSSIL TREE TRUNK 33I 



somewhat narrower so as to emphasize the favularian aspect as is 

 illustrated at about 80 cm from the base of the trunk in plate 7, 

 figure I. In this area the lateral cicatricules (parichnoi) of the 

 leaf scar are unusually clear in subepidermal impression, where 

 they appear to unite below in a narrow horseshoe form. 



The surface shown in plate 7, figure 3, is included in a fragment 

 of the counterpart impression of a portion of the trunk, at a level 

 about 90 cm from the base. It illustrates^ the distinctly vertical 

 alinement of the leaf cushions, which are becoming elongated in an 

 obovate-elliptical shape, the form of the leaf scars themselves, and 

 the hypodermal strands seen in the partially macerated upper cen- 

 tral area. The small portion, at a point a little lower on the trunk, 

 shown in figure i, includes an area in which the ribs are less macer- 

 ated and well rounded, with but slight constriction between the leaf 

 cushions. 



In plate 8 is shown, natural size, a portion of the actual carbon- 

 aceous residue of the trunk itself. The specimen, the impression 

 of which is in part shown in plate 7, figure 3, comes from near the 

 center of the trunk and is but 4 mm thick along the middle, the 

 thinner, fragile, carbonaceous borders being lost. It is, however, 

 particularly interesting as showing the outer surface of this portion 

 of the trunk. The outlines of the leaf cushions, which are observed 

 to be more prominent near their upper ends, are well defined, while 

 the leaf scars are in most cases recognizable. It is to be noted that 

 the cushions are nearly bilateral though the elongation approaches 

 the lepidodendroid form and the spirality of arrangement is dis- 

 tinct in the area on the upper right. 



Region of lepidodendroid form of leaf cushion. It has been 

 seen that in the lower areas examined the leaf cushions are alined 

 on very distinct longitudinal costae, from which they slightly pro- 

 trude. However, in passing upward we find a gradual change to a 

 leaf cushion form and relation more nearly characteristic of 

 Lepidodendron. Even at some distance below the middle of 

 the fossil the compressed cushions often present a lepidoden- 

 droid form near the border of the stem. An example of this 

 is shown in plate 7, figure 2, from an area but 85 cm from the 

 base, where we find, on the left, closely placed, indistinctly 

 rhomboidal impressions of cushions which are more clearly 

 spiral in arrangement and which appear to overlap somewhat 

 obliquely in the longitudinal sense. These approach a Bergeria 

 stage; but the cushions on the right, in the medal zone of 



^This figure is shown in light fr^m the left. 



